Cyclophosphamide is an established anti-cancer drug discovered in the 1950's, see Arnold, H. and Bourseaux, F., "Synthese Und Abbau Cytostatisch Wirksanfer Cyclischer N-Phosphamidester Des Bis-(.beta.-Chlorathyl)amins," Angewandte Chemie., 70, 539, 541 (1958). Cyclophosphamide is a common anti-cancer treatment which is now used to treat a variety of tumors in over 6 million people annually.
A related drug, the cyclohexylamine salt of phosphoramide mustard, was evaluated as a treatment for cancer in the 1960's. However, the clinical trials failed to show anti-tumor effect. See Nathanson, L., Hall, T. C., Rutenberg, A., and Shadduck, R. K., "Clinical Toxicologic Study of Cyclohexylamine Salt of N, N-bis(2-Chlorethyl) Phosphorodiamidic Acid (NSC-69945; OMF-59)," Cancer Chemother Rept., 51(1):35-39, (1967). Accordingly, phosphoramide mustard salt was abandoned as a treatment for cancer.
It was subsequently discovered that cyclophosphamide is not directly tumoricidal; instead the metabolites of cyclophosphamide exert the tumoricidal properties. Cyclophosphamide is metabolized via the hepatic crosomal oxidation to form the primary metabolite 4-OHCP/ALdp, 4-hydroxy-cyclophosphamide aldophosphamide. Subsequently chemical or enzymatic S-elimination generates two metabolites phosphoramide mustard, the acid form of the salt that was administered in clinical trials in the 1960's, and acrolein. It was also determined that the phosphoramide mustard has the greatest anti-tumor effect of the cyclophosphamide metabolites. In contrast, the acrolein produces the most side effects.
It would be desirable to have a highly active anti-tumor agent which when metabolized does not produce acrolein, yet is stable.